Effect of induction of subacute ruminal acidosis on milk fat profile and rumen parameters

High-concentrate diets can lead to subacute ruminal acidosis and are known to result in changes of the ruminal fermentation pattern and mammary secretion of fatty acids. The objective of this paper is to describe modifications in milk fatty acid proportions, particularly odd- and branched-chain fatty acids and rumen biohydrogenation intermediates, associated with rumen parameters during a 6-wk subacute ruminal acidosis induction protocol with 12 ruminally fistulated multiparous cows. The protocol involved a weekly gradual replacement of a standard dairy concentrate with a wheat-based concentrate (610 g of wheat/kg of concentrate) during the first 5 wk and an increase in the total amount of concentrate in wk 6. Before the end of induction wk 6, cows were switched to a control diet because 7 cows showed signs of sickness. The pH was measured continuously by an indwelling pH probe. Milk and rumen samples were taken on d 2 and 7 of each week. Data were analyzed using a linear mixed model and by principal component analysis. A pH decrease occurred after the first concentrate switch but rumen parameters returned to the original values and remained stable until wk 5. In wk 5 and 6, rumen pH values were indicative of increasing acidotic conditions. After switching to the control diet in wk 6; rumen pH values rapidly achieved normal values. Odd- and branched-chain fatty acids and C18:1 trans-10 increased with increasing amount of concentrate in the diet, whereas C18:1 trans-11 decreased. Four fatty acids [C18:1 trans-10, C15:0 and C17:0+C17:1 cis-9 (negative loadings), and iso C14:0 (positive loading)] largely correlated with the first principal component (PC1); with cows spread along the PC1 axis. The first 4 wk of the induction experiment showed variation across the second principal component (PC2) only, with high loadings of anteiso C13:0 (negative loading) and C18:2 cis-9,trans-11 and C18:1 trans-11 (positive loadings). Weeks 5 and 6 deviated from PC2 and tended toward the negative PC1 axis. A discriminant analysis using a stepwise approach indicated the main fatty acids discriminating between the control and acidotic samples as iso C13:0, iso C16:0, and C18:2 cis-9. trans-11 rather than milk fat content. or C18:1 trans-10; which have been used before as indicators of acidosis. This shows that specific milk fatty acids have potential in discriminating acidotic cases

Predictive value of liver cell dysplasia in needle liver biopsies for subsequent hepatocellular carcinoma in viral-induced chronic hepatitis and cirrhosis

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Effect of lactation stage on the odd- and branched-chain milk fatty acids of dairy cattle under grazing and indoor conditions

The pattern of odd- and branched-chain fatty acids (OBCFA) in milk fat reflects rumen microbial activity and proportions of different rumen microbial groups. Therefore, these milk fatty acids (FA) are used to predict rumen proportions of volatile fatty acids, duodenal flow of microbial protein, and occurrence of rumen acidosis. However, current models do not correct for the potential effects of lactation stage on the level of OBCFA in milk fat. Hence, the objectives of this study were 1) to describe progressive changes related to lactation stage in concentrations of milk FA, with emphasis on the OBCFA, using the incomplete gamma function of Wood, and 2) to analyze whether lactation curves of milk FA on the one hand and milk production or milk fat content on the other hand coincide through evaluation of the correlation between the parameters of the Wood functions fitted to individual animal data. Data were collected from 2 trials in which milk FA during lactation were monitored. The first experiment was a stable trial with 2 groups of 10 cows receiving 2 dietary treatments from wk 1 to 40 of lactation. The second experiment was a grazing trial with 9 cows that were followed during the first 18 wk of lactation. Lactation curves of milk production, milk fat content, and individual milk FA were developed using the incomplete gamma function of Wood for each of the 3 dietary strategies separately. For almost all of the milk FA, lactation curve shapes were similar for all 3 dietary treatments. The OBCFA with chain lengths of 14 and 15 carbon atoms followed the lactation curves of the short- and medium-chain milk FA, which increased in early lactation. The OBCFA with chain length of 17 carbon atoms decreased during the early lactation period, following the pattern of milk long-chain fatty acids. The short- and medium-chain milk FA and OBCFA in the early lactation period seemed to be negatively correlated with the starting milk production and milk fat content, but correlations were modest. Information of milk FA lactation curves should be incorporated in predictive and classification models based on these milk FA, to improve their performance

Relationships Among Early Lactation Milk Fat Depression, Cattle Productivity and Fatty Acid Composition on Intensive Dairy Farms in Northern Italy

An observational study was conducted on three northern Italy Holstein dairy herds to evaluate the impact of milk fat depression (MFD, defined as milk fat lower than 3.2) on milk production and fatty acids (FA) composition in order to investigate the practical consequences and the possible origin of this phenomenon. The diet composition and the individual milk production and composition, were monitored during the first six months of lactation. Two virtual groups were created in each farm on the basis of the milk fat levels observed during the first two months of lactation (higher or lower than 3.2). Individual milk samples were taken from 16 animals /group/farm for composition and fatty acid analysis. The diet of Farm A, characterized by the highest average prevalence of MFD (33.1%), showed the highest acidogenic attitude (high NFC, low NDF, low peNDF8). The milk fat level differed significantly per group over time in all farms. Cattle with MFD showed tendentially lower energy corrected milk output and greater concentrations of C12:0÷C15:0, C18:1trans10, total polyunsaturated, total odd chain (OCFA), total n-6 as well as OCFA/branched chain fatty acids, and C18:1trans10/C18:1trans11 ratios. Farm A milk fat showed higher values of C12:0, C13:0, C14:0 and C15:0. It appears that MFD cattle are characterized by lower mammary energy output and a milk FA profile similar to cattle fed acidogenic diets, thus suggesting an alteration in the rumen fermentation patterns, as occurs in acidotic cattle